Messages in this thread | | | Date | Thu, 12 Nov 2015 09:18:54 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v2 4/4] x86/entry/64: Bypass enter_from_user_mode on non-context-tracking boots |
| |
* Andy Lutomirski <luto@kernel.org> wrote:
> On CONFIG_CONTEXT_TRACKING kernels that have context tracking > disabled at runtime (which includes most distro kernels), we still > have the overhead of a call to enter_from_user_mode in interrupt and > exception entries. > > If jump labels are available, this uses the jump label > infrastructure to skip the call. > > Signed-off-by: Andy Lutomirski <luto@kernel.org> > --- > arch/x86/entry/calling.h | 15 +++++++++++++++ > arch/x86/entry/entry_64.S | 8 ++------ > 2 files changed, 17 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h > index 3c71dd947c7b..e32206e09868 100644 > --- a/arch/x86/entry/calling.h > +++ b/arch/x86/entry/calling.h > @@ -1,3 +1,5 @@ > +#include <linux/jump_label.h> > + > /* > > x86 function call convention, 64-bit: > @@ -232,3 +234,16 @@ For 32-bit we have the following conventions - kernel is built with > > #endif /* CONFIG_X86_64 */ > > +/* > + * This does 'call enter_from_user_mode' unless we can avoid it based on > + * kernel config or using the static jump infrastructure. > + */ > +.macro CALL_enter_from_user_mode > +#ifdef CONFIG_CONTEXT_TRACKING > +#ifdef HAVE_JUMP_LABEL > + STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0 > +#endif > + call enter_from_user_mode > +.Lafter_call_\@: > +#endif > +.endm > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index a55697d19824..9d34d3cfceb6 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -520,9 +520,7 @@ END(irq_entries_start) > */ > TRACE_IRQS_OFF > > -#ifdef CONFIG_CONTEXT_TRACKING > - call enter_from_user_mode > -#endif > + CALL_enter_from_user_mode > > 1: > /* > @@ -1066,9 +1064,7 @@ ENTRY(error_entry) > * (which can take locks). > */ > TRACE_IRQS_OFF > -#ifdef CONFIG_CONTEXT_TRACKING > - call enter_from_user_mode > -#endif > + CALL_enter_from_user_mode > ret > > .Lerror_entry_done: > -- > 2.5.0 >
hm, this patch does not apply to latest -tip:
patching file arch/x86/entry/entry_64.S Hunk #1 FAILED at 520. Hunk #2 FAILED at 1066. 2 out of 2 hunks FAILED -- rejects in file arch/x86/entry/entry_64.S
am I missing some dependency, or are they against an older tree?
Thanks,
Ingo
| |